Abstract:

Orchard floor management (OFM) practices can improve soil function and alter
the soil biological community. Soil function is dependent on soil forming materials and
on management practices but little is known about how OFM affect orchard soil quality,
fertilizer N uptake, or tree growth and production.
Research plots were located in Corvallis, OR (LB) (Malus x domestica ‘Fuji’
grafted on dwarfing M26EMLA rootstock) and Hood River, OR (HR) (M. x domestica
‘Red Delicious’ grafted on M7EMLA rootstock). Treatments were begun in 2001 in a
splitplot
completely randomized design with 3 replications. Main plot treatments were
weed control method, cultivation and postemergent
herbicide. Sub plot treatments were
an unamended control, bark mulch, compost, and vetch/barley mown and raked into the
tree row. Depleted 15 (NH4)2SO4 was applied to a single tree in each plot at bud break.
Trees were destructively harvested in the fall of 2003.
Weed control method had no effect on soil organic matter (SOM) content and few
effects on other soil properties. There were no significant differences between cultivation
and herbicide in % N derived from fertilizer (NDFF) in the trees despite the potential for
altered mineralization rates with these treatments. Growth of young trees at HR was
reduced by cultivation because weed growth was not controlled.
Compost increased SOM content at both LB and HR. Compost also had the most
consistent effect on other soil properties and soil respiration. Amendment did not affect
the % N in the trees, but vetch/barley amendment increased % NDFF at HR and fertilizer
uptake efficiency (FUE) at LB. % NDFF and FUE were low in compost amended plots.
Trees in compost acquired N from sources other than fertilizer.
Yield was increased by bark mulch and decreased by compost at HR. At LB
vegetative growth was increased by compost. The relationships between specific changes
in the soil and improved orchard performance are still unclear. However, there are
correlations between growth and soil characteristics that suggest that alternative
management practices, especially compost amendment, do have the potential to decrease
the need for chemical fertilizer inputs.